Consider this example: You are home, laid out flat with bad back trouble. The only thing that keeps your flagging spirit from sinking is the pay-per-view movie showing on your television through the paid courtesy of your cable television (CATV) service provider. The movie has ended, but it is the first of a trilogy and you would really like to order and watch the sequels. But this is a Herculean task to accomplish. With your bad back, it is going to be a lot of trouble to get out of bed, to find the telephone, to remember and to dial the pay-per-view telephone number, and to get yourself back into the least uncomfortable position that your back will allow for more movie watching.
Wouldn't it be nice if you could just use a remote control unit with your television to request the delivery of the second and third movie? So, what is the hang up? The hang up is that no cost effective transport system exists for the transmission of signals from a device (such as your set top box) to a signal destination (such as your CATV service provider, video server, etc.) so that you could order your next movie by simply using the remote control unit. Those skilled in the art will recognize the term "set top box" as referring to those elements of the device (whether disposed within a set top box or not) that serve as an interface system between the device and the fiber-and-coax network that transports the signals.
To understand the problems associated with ordering a movie through use of your television's remote control unit, a general description of CATV service is provided by reference to FIG. 1. FIG. 1 is a block diagram of a video signal delivery system. Generally, the delivery or transmission of a set of video or data signals from a video signal source (such as a CATV service) to a device (such as your set top box) is referred to as "downstream" delivery, a "downstream path" or a "forward path". As illustrated in FIG. 1, a downstream path 5 generally has its beginning at a video signal source 10 that transmits a set of video signals to an optical transmitter 12. For ease of explanation, the term "optical transmitter" is used herein to encompass the elements or mechanisms that receive the video signals from the video signal source 10, that convert, modulate, carry, amplify and/or split the video signals (as necessary) so as to optically transport the signals from the video signal source 10 to one or more local distribution units such as broadband communications module 14. A broadband communications module is also referred to as an analog video unit, an analog network unit, an optical receiver, or in some cases, as an optical node. A broadband communications module 14 typically converts the video signals from optical to electrical, and transmits the video signals through a bandpass filter 15 over coaxial cable to a relatively large number of devices. One such device is device 16 which is also referred to as a set top box, home controller unit, cable ready TV, or residential gateway. The transmission of a set of video signals from a broadband communications module 14 over coaxial cable to a device 16 is referred to as a "drop". Thus, FIG. 1 illustrates a downstream path 5 for the transmission of a set of video signals from a video signal source 10, to an optical transmitter 12, to a broadband communications module 14, to a filter 15 and for ultimate drop to a device 16. The downstream path 5 has been generally described in the context of the delivery of a movie to a subscriber's television, but the description is applicable as well to other video or data signal delivery such as broadcast television, or video, near video on demand, InterNet access, interactive shopping and similar delivery services. For example, a video signal source may include a video server, modulator, headend or a content provider. A device may include a personal computer, set top box, digital receiver, home controller terminal or gateway.
Generally, the delivery or transmission of a set of video or data signals from a device to a video/data signal destination is referred to as "upstream" delivery or a "return path". As illustrated in FIG. 1, a return path 20 generally has its beginning at a device 16 that transmits a set of video or data signals over coaxial cable to a bandpass filter 15. Typically, the filter recognizes the signals as return path signals, and transmits the signals to other elements or mechanisms for ultimate delivery to their destination. As will be discussed in more detail below, FIG. 1 illustrates a return path 20 for the transmission of a set of video signals from a device 16, to a filter 15 (with return path amplification) to a Fabry-Perot return path laser 22, to a return path concentrator 24, to a central processing station 26, and for ultimate delivery to a video/data signal destination 28. The return path 20 has been generally described in the context of the order of a movie from a subscriber's television, but the description is applicable as well to other video or data signal delivery from a source such as video channel selection, impulse pay per view requests, shopping requests, and enhanced video control signals for stopping, reversing or accelerating the playback of a video or data source.
In the above description of a downstream path 5 and a return path 20, reference was made to elements such as the video signal source, etc., but the actual mechanism for transporting the video or data signals among the elements was not spelled out in all cases. This omission was deliberate so as to provide a little historical discussion at this point. In the early days of cable television, CATV service providers used coaxial cable as the mechanism for transporting the video signals from the video signal source to the device. Hence, the term "cable company". But coaxial cable has its limitations as a transport mechanism, and cable companies soon realized the advantages offered by fiber optics to the transport of video signals. Most CATV service now is provided over a fiber-and-coax network, which is a hybrid network that provides duplex voice and data circuits and simplex broadband channels to the public. Optical fibers are used for signal transport from a video signal source to local distribution points such as the illustrated broadband communications module 14. At such a local distribution point, the signal streams are converted from optical signals to electrical signal streams, and distributed ("dropped") to individual homes over shared coaxial cable.
CATV service providers recognized the potential of fiber optics for the transport of video/data signals and provided fiber-and-coax networks for the downstream path of delivery of video signals. But, for the most part, CATV service providers have until recently ignored and failed to provide a signaling return path for video/data signals. The fiber-and-coax networks generally were not set up to handle video/data signals that were transmitted from a device 16 (such as your set top box) back through the optical transmitter 12 to the video signal source 10. One reason that CATV service providers (and others) ignored the signaling return path is that, until recently, there was little possibility that a subscriber would have information to transmit by return path. In its early days, CATV was developed for subscribers who lived outside the reach of over-the-air broadcast television stations. These early subscribers paid a flat fee for service. No signaling return path was necessary.
Another reason that CATV service providers (and others) ignored the return path is based on economics. Alterations or additions to a fiber-and-coax network to provide a signaling return path have not been cost justified for several reasons. For example, the proposed alterations and additions would be extensive and expensive. Further, until recently, it has been believed that even with "pay-per-view services" a subscriber would have only a small amount of information to transmit by return path. Thus, the cost did not justify the changes that were necessary.
But times have changed. The personal computer has changed the attitude of the public. Surveys have demonstrated that the majority of Americans cannot imagine living without a personal computer. Through a personal computer, a user has access to all sorts of information. Through mechanisms such as local area networks, wide area networks, the InterNet, and others, a user is able to interact with others who are in the network and to interact with computer programs, information and services. In other words, with a networked computer, a user has a "downstream path" for the receipt of information, and a "return path" for the transmission of information. Having been educated by networked computers to the advantages of the exchange of information, a user is surprising dismayed to find that CATV service generally is only "one-way", i.e., downstream path only. There is no convenient, efficient, economical return path. How Neanderthal!
Within the next few years, the need for multichannel, bi-directional video/data transmissions will multiply within every home and enterprise because of the coming integration of video/data information into the conduct of business, the process of learning and other aspects of life in the twenty-first century.